1. Field of the Invention
The present invention relates to an anti-entrapment system provided with a capacitance sensor for preventing entrapment of an object.
2. Background Art
Anti-entrapment systems use various types of sensors to detect pinching of an object such as a human body part. For example, in automobiles, sensors are used for pinch sensing at electrically operated doors, windows, hatches, decks, hoods, lids, and the like.
A pinch sensor detects pinching an object by a translating device such as a window, door, sunroof, etc. In operation, the pinch sensor generates a pinch sensor signal in response to the object such as a person's finger being pinched by a translating device such as a window as the window is closing. In response to the pinch sensor signal, a controller controls the window to reverse direction and open in order to prevent further pinching of the person's finger. As the window is opening, the person may remove his finger from the window opening between the top edge of the window and the window liner.
Motor current sensors, infrared beam sensors, and continuous switch sensors have been used as pinch sensors in anti-entrapment systems. A problem with these types of pinch sensors is that they require a relatively large amount of pinching of the object to take place before they detect pinching of the object.